Generally, a semiconductor package is fabricated by attaching a semiconductor die to a circuit board (die bonding). The circuit board and the semiconductor die may then be electrically connected. In accordance with one method, conductive wires (wire bonding) may be used to electrically connect the circuit board and the semiconductor die. The semiconductor die and the conductive wires may then be encapsulated by an encapsulant (encapsulation).
The wire bonding process may includes the following steps: creating a free air ball (FAB) at one end of a conductive wire protruding downwardly through a lower end of a capillary using an electric flame-off (ER)) tip; moving the capillary toward a bond pad of a semiconductor die and primarily bonding the FAB to the bond pad (ball bonding); and moving the capillary toward a pattern of a circuit board and secondarily bonding the distal end of the conductive wire to the pattern (stitch bonding).
The conductive wire may be made of gold. In some cases, the gold wire is currently replaced by a cheaper copper wire. Since the Vickers hardness of the copper wire and its FAB is relatively high compared to that of the gold wire and its FAB, the use of the copper wire increases the probability of damage to the bond pad of the semiconductor die. That is, the bond pad is apt to crack when the relatively hard FAB of the copper wire is brought into close contact with the bond pad. Particularly, when the copper wire is applied to a low-dielectric constant (k) semiconductor device, weak active regions of the semiconductor device may lead to damage or cracking of the semiconductor device. Although the price of a copper wire is about one hundredth of that of a gold wire, the relatively high hardness of the copper wire increases the number of defects during wire bonding.
Therefore, a need existed to provide a system and method to overcome the above problem. The system and method would provide a wire bonder which reduces the hardness of a free air ball of a conductive wire.